Cross point memory arrays, methods of manufacturing the same, masters for imprint processes, and methods of manufacturing masters

ABSTRACT

A cross point memory array includes a structure in which holes are formed in an insulating layer and a storage node is formed in each of the holes. The storage node may include a memory resistor and a switching structure. The master for an imprint process used to form the cross-point memory array includes various pattern shapes, and the method of manufacturing the master uses various etching methods.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to Korean Patent Application No.10-2008-0097788, filed on Oct. 6, 2008, Korean Patent Application No.10-2008-0111218, filed on Nov. 10, 2008, and Korean Patent ApplicationNo. 10-2009-0012118, filed on Feb. 13, 2009, in the Korean IntellectualProperty Office. The entire contents of each of these applications areincorporated herein by reference.

BACKGROUND

1. Field

One or more example embodiments relate to cross point memory arrays,methods of manufacturing the same, masters for imprint processes, andmethods of manufacturing masters. More particularly, one or more exampleembodiments relate to cross point memory arrays including a variableresistance material as a storage node, methods of manufacturing thesame, masters for imprint processes, which are used to manufacture crosspoint memory arrays, and methods of manufacturing masters.

2. Description of the Related Art

Conventional semiconductor memory arrays include a plurality of unitmemory cells. An example of a volatile semiconductor memory is a dynamicrandom access memory (DRAM). In a conventional DRAM, each unit memorycell includes a switch and a capacitor. Conventional DRAMs arerelatively highly integrated and have relatively fast operating speeds.But, DRAMs are volatile in that after power to the DRAM is turned off,all data stored in the DRAM is lost.

A conventional flash memory, on the other hand, is an example of anon-volatile memory device. In a conventional flash memory device alldata stored in the non-volatile memory device is retained even afterpower to the non-volatile memory device is turned off. Conventionalflash memories have non-volatile properties, but have lower integrationdegree and slower operating speeds as compared to conventional DRAMs.

At present, non-volatile memory devices, such as magnetic random accessmemory (MRAM), ferroelectric random access memory (FRAM), phase-changerandom access memory (PRAM), and resistance random access memory (RRAM)are being studied. In one example, to store data a RRAM uses a variableresistance property of a transition metal oxide material, for example, aproperty in which the resistance of the transition metal oxide materialvaries according to the state of the RRAM.

RRAMs have been studied based on a cross point array structure in whicha plurality of lower electrodes and a plurality of upper electrodescross one another. A storage node is formed at each point in which theplurality of lower electrodes and the plurality of upper electrodescross one another. Random access is possible in the cross point arraystructure, and thus, data reading and writing may be performed moreeasily. However, when reading and writing data, a current path is formedbetween the cross point array structure and a storage node that isadjacent to the cross point array structure, thereby resulting in aleakage current. To reduce the leakage current in the cross point arraystructure, a switching structure is formed together with the storagenode.

Various technologies for transferring semiconductor patterns tomanufacture a semiconductor device, such as a resistive memory device,have been developed. The technology that is mostly used for transferringsemiconductor patterns is photolithography such as electron beam(E-beam) lithography technology and X-ray exposure technology usingradiation light. These types of photolithography are used to manufacturea mask for photolithography and to form fine patterns. In thesetechnologies, as semiconductor patterns become more precise, the costfor manufacturing a semiconductor device increases. In addition, inE-beam lithography photolithography, patterns have a two-dimensional(2D) structure in which the shape of patterns formed in an exposedregion and the shape of patterns formed in an unexposed region arerelatively simple. Thus, there is a limitation in forming variouspatterns.

Nano-imprint lithography (NIL) has been found to be a relativelyeffective and relatively economical alternative technology for formingpatterns. NIL is a technology suggested for performing a nano-process(e.g., about 1 nm to about 100 nm, inclusive) as an ultra-fine process.In NIL, mold patterns are directly transferred onto a substrate by usinga press method. A thermoplastic resin or a photocurable resin is coatedon the substrate, pressurized with a nano-sized mold by using heat orultraviolet (UV) rays, and cured to transfer the mold patterns. By usingNIL, a stepped portion may be formed more conveniently on a substrate tobe processed. A general photolithography process is finished with a onepress transferring process, and thus, NIL is more effective for forminga multi-stepped shape. It has also been reported that NIL may be used ina process of manufacturing an electronic device such as a metal oxidesemiconductor field effect transistor (MOSFET) or an optical device,instead of the general photolithography process.

SUMMARY

One or more example embodiments provide cross point memory arrays andmethods of manufacturing the same.

One or more example embodiments also provide masters for imprintprocesses, in which various patterns are formed, and methods ofmanufacturing the same.

According to at least one example embodiment, a cross point memory arrayincludes a plurality of bottom electrodes formed on a substrate to beparallel with one another, and a plurality of top electrodes formed tobe parallel with one another and to cross the bottom electrodes. Thecross point memory array further includes an insulating layer interposedbetween the bottom electrodes and the top electrodes. The insulatinglayer includes a hole formed at each point where the bottom electrodesand the top electrodes cross one another. Each hole exposes a portion ofa surface of a bottom electrode. Still further, the cross point memoryarray includes a storage node formed in each hole. The storage nodeincludes a memory resistor, an intermediate electrode layer, and aswitching structure formed sequentially in each hole. The memoryresistor is formed on a bottom and a sidewall of each of the holes.

According to at least some example embodiments, the memory resistor maybe a material having two or more resistances according to the size of anapplied pulse voltage. The memory resistor may be formed of a transitionmetal oxide material. For example, a transition metal oxide material mayinclude nitrogen (Ni) oxide, titanium (Ti) oxide, hafnium (Hf) oxide,zirconium (Zr) oxide, zinc (Zn) oxide, tungsten (W) oxide, cobalt (Co)oxide, copper (Cu) oxide, niobium (Nb) oxide, or a material including atleast one selected from the group including: Ni oxide, Ti oxide, Hfoxide, Zr oxide, Zn oxide, W oxide, Co oxide, Cu oxide, and Nb oxide.The switch structure may include a diode having an n-type oxidesemiconductor layer and a p-type oxide semiconductor layer.

At least one other example embodiment provides a method of manufacturinga cross point memory array. According to at least this exampleembodiment, a plurality of bottom electrodes are formed on a substrateto be parallel with one another, and an insulating layer is formed onthe bottom electrodes. A plurality of holes are formed in the insulatinglayer at positions corresponding to the bottom electrodes by performinga nano-imprint process. A storage node is formed on a bottom and asidewall of each of the holes, and a plurality of top electrodes areformed to be parallel with one another at positions corresponding to theholes.

At least one other example embodiment provides a master for an imprintprocess. According to at least this example embodiment, the masterincludes a first type pattern and a second type pattern. The first typepattern and the second type pattern may have different shapes.

According to at least some example embodiments, the first type patternand the second type pattern may include at least one pattern selectedfrom the group including an inclination pattern, a vertical pattern, anda rounded pattern. The master may include a multi-layered structure, andthe first type pattern and the second type pattern may be formed indifferent layers. The widths of the first type pattern and the secondtype pattern may be different. The master may include a first layer, asecond layer, and a third layer. The second layer and the third layermay be formed sequentially on the first layer, and the first typepattern is formed in the third layer. The second type pattern is formedin the second layer. The width of the second type pattern may be lessthan that of the first type pattern. The second layer may includesilicon oxide or silicon nitride, and the third layer may includesilicon.

At least one other example embodiment provides a method of manufacturinga master for an imprint process. According to at least this exampleembodiment, a substrate is prepared and a mask layer is formed such thata portion of a surface of the substrate is exposed through the masklayer. A first etching process is performed to form a first type patternin the exposed surface of the substrate, and a second etching process isperformed to form a second type pattern in the substrate.

According to at least some example embodiments, the first etchingprocess and/or the second etching process may include at least oneprocess selected from the group including a dry etching process and awet etching process. For example, the first etching process may be a wetetching process, and the first type pattern may be an inclinationpattern. The surface of the substrate may include Si (100), and the wetetching process may be an etching process using a potassium hydroxide(KOH) or tetramethylammonium hydroxide (TMAH) solution.

According to at least some example embodiments, the first etchingprocess may be a dry etching process, and the first type pattern may bea vertical pattern. The surface of the substrate may include Si (100),and the dry etching process may be an etching process using, forexample, Cl₂, or CF₄/O₂ gas.

According to at least some example embodiments, the first etchingprocess may be a wet etching process, and the first type pattern may bea rounded pattern. The surface of the substrate may include Si, and thewet etching process may be an etching process using, for example,HF/HNO₃/H₂O or HF/HNO₃/CH₃COOH.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of example embodiments, takenin conjunction with the accompanying drawings of which:

FIG. 1 is a perspective view of a cross point memory array according toan example embodiment;

FIG. 2 is a cross-sectional view of the cross point memory array of FIG.1, taken along line V-V1;

FIG. 3 is a graph showing example current versus voltage (I-V)characteristics of a resistance material of a memory resistor of thecross point memory array shown in FIG. 1;

FIG. 4 is a graph showing an example area of a switch structure versuscurrent to be supplied to the cross point memory array at differentcurrent densities;

FIGS. 5A through 5F illustrate a method of manufacturing the cross pointmemory array shown in FIG. 1 according to an example embodiment;

FIGS. 6A through 6G illustrate a method of manufacturing the cross pointmemory array shown in FIG. 1 according to another example embodiment;

FIG. 7 illustrates a master for an imprint process according to anexample embodiment;

FIGS. 8A through 8E illustrate a method of manufacturing the mastershown in FIG. 7 according to an example embodiment;

FIGS. 9A through 9E illustrate a method of manufacturing a master for animprint process according to another example embodiment;

FIGS. 10A through 10E illustrate a method of manufacturing a master foran imprint process according to another example embodiment; and

FIG. 11 illustrates an example stamp formed using the master shown inFIG. 7.

DETAILED DESCRIPTION

Various example embodiments will now be described more fully withreference to the accompanying drawings in which some example embodimentsare shown. In the drawings, the thicknesses of layers and regions areexaggerated for clarity.

Detailed illustrative example embodiments are disclosed herein. However,specific structural and functional details disclosed herein are merelyrepresentative for purposes of describing example embodiments.Embodiments may, however, may be embodied in many alternate forms andshould not be construed as limited to only the example embodiments setforth herein.

Accordingly, while example embodiments are capable of variousmodifications and alternative forms, embodiments thereof are shown byway of example in the drawings and will herein be described in detail.It should be understood, however, that there is no intent to limitexample embodiments to the particular forms disclosed, but on thecontrary, example embodiments are to cover all modifications,equivalents, and alternatives falling within the scope of theembodiments described herein. Like numbers refer to like elementsthroughout the description of the figures.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, these elements should notbe limited by these terms. These terms are only used to distinguish oneelement from another. For example, a first element could be termed asecond element, and, similarly, a second element could be termed a firstelement, without departing from the scope of example embodiments. Asused herein, the term “and/or,” includes any and all combinations of oneor more of the associated listed items.

It will be understood that when an element or layer is referred to asbeing “formed on,” another element or layer, it can be directly orindirectly formed on the other element or layer. That is, for example,intervening elements or layers may be present. In contrast, when anelement or layer is referred to as being “directly formed on,” toanother element, there are no intervening elements or layers present.Other words used to describe the relationship between elements or layersshould be interpreted in a like fashion (e.g., “between,” versus“directly between,” “adjacent,” versus “directly adjacent,” etc.).

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of exampleembodiments. As used herein, the singular forms “a,” “an,” and “the,”are intended to include the plural forms as well, unless the contextclearly indicates otherwise. It will be further understood that theterms “comprises,” “comprising,” “includes,” and/or “including,” whenused herein, specify the presence of stated features, integers, steps,operations, elements, and/or components, but do not preclude thepresence or addition of one or more other features, integers, steps,operations, elements, components, and/or groups thereof.

Reference will now be made in detail to embodiments, examples of whichare illustrated in the accompanying drawings, wherein like referencenumerals refer to the like elements throughout. In this regard, thepresent embodiments may have different forms and should not be construedas being limited to the descriptions set forth herein. Accordingly, theexample embodiments are merely described below, by referring to thefigures, to explain aspects of the present description.

FIG. 1 is a perspective view of a cross point memory array according toan example embodiment. FIG. 2 is a cross-sectional view of the crosspoint memory array of FIG. 1, taken along line V-V1.

Referring to the example embodiment shown in FIGS. 1 and 2, a pluralityof bottom electrodes 301 are formed on a substrate 300. The bottomelectrodes 301 are formed to be in parallel with one another. Aplurality of top electrodes 306 are formed to cross the bottomelectrodes 301, and to be in parallel with one another. A storage nodeis formed at each cross point between the bottom electrodes 301 and thetop electrodes 306. The storage node includes, inter alia, a memoryresistor 303.

An insulating layer 302 is interposed between the bottom electrodes 301and the top electrodes 306. A hole h is formed through the insulatinglayer 302 at each point where the bottom electrodes 301 and the topelectrodes 306 cross one another. The bottom of each hole h exposes aportion of the surface of a corresponding bottom electrode 301. Theholes h may have various shapes such as a cone shape, a cylindricalshape, a pyramidal shape, an asymmetrically polygonal shape, etc.

As shown in FIGS. 1 and 2, the memory resistor 303, an intermediateelectrode 304, and a switch structure 305 are formed sequentially aslayers in each hole h. For example, the memory resistor 303 may beformed as a layer on the bottom and the sidewall of the holes h throughthe insulating layer 302. The intermediate electrode 304 and the switchstructure 305 are formed sequentially on the memory resistor 303. Thetop electrode 306 is formed on the switch structure 305.

The substrate 300 may be a silicon (Si) substrate used in a generalsemiconductor device or an insulating substrate made of glass orplastic.

The bottom electrode 301, the intermediate electrode 304, and the topelectrode 306 may be formed of an electrode material such as aluminum(Al), hafnium (Hf), zirconium (Zr), zinc (Zn), tungsten (W), cobalt(Co), gold (Au), platinum (Pt), ruthenium (Ru), iridium (Ir), titanium(Ti), or a conductive metal oxide.

The insulating layer 302 may be formed of an insulating material thatreduces and/or prevents the transmission of current. For example, theinsulating layer 302 may be silicon dioxide (SiO₂), silicon nitride(Si₃N₄), aluminum oxide (Al₂O₃), etc.

The memory resistor 303 may be formed of a variable resistance materialthat is used in a variable resistance memory devices in which thestorage and erasure of information is performed by varying resistance.The memory resistor 303 may be formed of a unipolar material in whichthe storage and erasure of information is performed by applying pulsevoltages in one direction. That is, for example, the memory resistor 303may be formed of a unipolar material in which the storage and erasure ofinformation is performed by applying pulse voltages having the samepolarity. The unipolar material may be, for example, a transition metaloxide material such as nitrogen (Ni) oxide, titanium (Ti) oxide, hafnium(Hf) oxide, zirconium (Zr) oxide, zinc (Zn) oxide, tungsten (W) oxide,cobalt (Co) oxide, copper (Cu) oxide, niobium (Nb) oxide, or a materialincluding at least one selected from the group including: Ni oxide, Tioxide, Hf oxide, Zr oxide, Zn oxide, W oxide, Co oxide, Cu oxide, and Nboxide. According to at least some example embodiments, the transitionmetal oxide material may be nickel oxide (NiO), titanium dioxide (TiO₂),hafnium oxide (HfO), zirconium oxide (ZrO), zinc oxide (ZnO), tungstentrioxide (WO₃), cobalt oxide (CoO), copper oxide (CuO), Nb₂O₅, or acompound including at least one selected from the group including: NiO,TiO₂, HfO, ZrO, ZnO, WO₃, CoO, CuO, and Nb₂O₅.

The switch structure 305 may be formed as a non-ohmic structure such asa diode, a Zener diode, a varistor, or a threshold voltage switchingelement. In other words, the switch structure 305 may be an oxide diodehaving a multi- or bi-layer structure of an n-type oxide semiconductorlayer and a p-type oxide semiconductor layer.

When the switch structure 305 is a diode, the switch structure 305controls the direction of current that flows through the memory resistor303. The switch structure 305 allows current to flow through the memoryresistor 303 in one direction, but controls the flow of current inanother direction to reduce and/or prevent leakage current that mayoccur in a cross point array structure.

Example operating characteristics of a memory resistor 303 formed of aunipolar material are shown in the current versus voltage (I-V) graph ofFIG. 3.

FIG. 3 is a graph showing example I-V characteristics of a resistancematerial of the memory resistor 303 of the cross point memory arrayshown in FIG. 1.

Referring to FIG. 3, if the sizes of voltages to be applied to thebottom electrode 301 and the top electrode 306 are increased graduallyfrom about 0 V, currents increase in proportion to the voltages along agraph G1. However, if a voltage equal to about V1 is applied to thebottom electrode 301 and the top electrode 306, the resistance of thememory resistor 303 increases substantially, and current is reduced. Ifa voltage in the range of between about V1 and about V2 is applied tothe bottom electrode 301 and the top electrode 306, current that flowsthrough the memory resistor 303 increases along graph G2. If a voltagegreater than or equal to about voltage V2 (V2>V1) is applied to thebottom electrode 301 and the top electrode 306, the resistance of thememory resistor 303 is suddenly reduced, and current increases alonggraph G1.

In a general resistive memory device, a reset current that varies fromgraph G1 indicative of a low resistance state (LRS) to graph G2indicative of a high resistance state (HRS) (e.g., current at voltage V1shown in the graph G1) is reduced as the size of unit cells is reduced.The reset current may be reduced by reducing the size of the unit cellsto reduce power consumption of the cross point memory array and/or toimprove the integration degree of the cross point memory array.

Meanwhile, the characteristic of current that flows through the storagenode is controlled by the switch structure 305. When the switchstructure 305 such as a diode is used, the size of current applied tothe storage node is related to the area of the switch structure 305. Inother words, when relatively large current is used to set or reset thestorage node, the size of current may be reduced by increasing the sizeof the switch structure 305 formed between the top electrode 306 and theintermediate electrode 304. In this case, referring back to FIG. 2, thearea of the memory resistor 303 is similar or substantially similar tothe area of the switch structure 305, but the area of the memoryresistor 303 that contacts the bottom electrode 301 is limited by theinsulating layer 302. Thus, the effective area of the memory resistor303 that acts as the storage node corresponds to the exposed area of theinsulating layer 302.

FIG. 4 is a graph showing an example area of a switch structure versuscurrent to be supplied to the cross point memory array at differentcurrent densities.

Referring to FIG. 4, in the case of a circular switch having an area ofabout 10⁻² μm², assuming that the variable resistance material of amemory resistor is switched at a current of about 10⁻⁴ A (0.1 mA), thecurrent density is about 106 A/cm². This applies to a rectangular switchhaving opposite sides with a length of about 100 nm. However, when theswitch structure 305 is formed as a three-dimensional (3D) structure ina corresponding hole h, the area of the switch structure 305 isincreased (e.g., greatly or substantially increased). According to atleast some example embodiments, the switch structure 305 is formed as a3D structure. In this case, the area of the bottom of the switchstructure 305 is about 10⁻² μm², but the total area thereof is about10⁻¹ μm². As a result, a switching current of about 10⁻⁴ A may flow at acurrent density of about 105 A/cm². That is, for example, the currentdensity may be reduced by about 1/10 as compared to a switch having a 2Dstructure. Accordingly, in a resistive memory device according to atleast this example embodiment, the switch structure 305 is formed as a3D structure while the area of the storage node does not increase sothat a more stable switching current with a relatively high integrationdegree may be maintained.

Thus, in cross point memory arrays, an electric potential for drivingthe storage node is applied to the bottom area of the intermediateelectrode 304 in which the memory resistor 303 contacts the intermediateelectrode 304. Thus, the aspect ratio (AR) of the hole h of theinsulating layer 302 is controlled to improve the integration degree ofthe cross point memory array. In addition, a contact side in which theswitch structure 305 and the intermediate electrode 304 contact eachother is formed as a 3D structure, and the size of the contact side islarger (e.g., substantially larger) than the cross-sectional area of thehole h so that the current density for switching the resistive memorydevice may be improved.

Hereinafter, methods of manufacturing boss point memory arrays accordingto example embodiments will be described in detail with reference toFIGS. 5A through 5F and FIGS. 6A through 6G.

FIGS. 5A through 5F illustrate a method of manufacturing a cross pointmemory array such as the cross point memory array shown in FIG. 1according to an example embodiment.

Referring to FIG. 5A, an electrode material is coated on the substrate300 and patterned to form the bottom electrode 301. The electrodematerial may be Al, Hf, Zr, Zn, W, Co, Au, Pt, Ru, Ir, Ti, or conductivemetal oxide such as indium zinc oxide (IZO) or indium tin oxide (ITO).

Referring to FIG. 5B, an insulating material 302 may be coated on thebottom electrode 301 using a method of forming a thin film such as spincoating, dispensing, spray coating, etc. A nano-imprint process isperformed using a stamp S in which a solid shape such as a circularcylinder shape, a cone shape, or a pyramidal shape is formed, therebyforming patterns defining the holes h. As shown in FIG. 5B, the holes hhave a shape inverse to the shape of the stamp S at positions on thebottom electrode 301.

After the nano-imprint process is performed, additional processes, suchas an ashing or a similar process, may be performed to expose the bottomelectrode 301.

FIG. 5C is a cross-sectional view of a structure in which the patternsare formed as the insulating layer 302 after performing the nano-imprintprocess.

Referring to FIG. 5C, an organic material or an inorganic materialhaving sufficient (e.g., excellent) insulating properties, such ashydrogen silsesquioxane (HSQ) or photocurable epoxy silane resin (PES),may be used as an insulating material formed on the bottom electrode 301to reduce and/or prevent leakage current and/or a short circuit betweenthe resistance bodies 303 in which information is stored.

The stamp S used in the nano-imprint process may be manufactured using amaster that is manufactured with various materials such as Si, polymer,metal, quartz, etc. For example, the stamp S may be manufactured bycopying patterns by coating polymer on the master, or by copyingpatterns in the form of metal by plating, or by performing a processsuch as an etching process after the patterns are transferred onto aquartz, glass, or another Si wafer by using the master and polymer.

Referring to FIG. 5D, after performing the nano-imprint process avariable resistance material is coated in the hole h to form the memoryresistor 303. The memory resistor 303 may be formed of a unipolarmaterial in which the storage and erasure of information is performed byapplying pulse voltages in one direction (e.g., by applying voltageshaving the same polarity). The unipolar material may be, for example, atransition metal oxide material such as Ni oxide, Ti oxide, Hf oxide, Zroxide, Zn oxide, W oxide, Co oxide, Cu oxide, Nb oxide, or a materialincluding at least one selected from the group including: Ni oxide, Tioxide, Hf oxide, Zr oxide, Zn oxide, W oxide, Co oxide, Cu oxide, and Nboxide.

After the memory resistor 303 is formed, Al, Hf, Zr, Zn, W, Co, Au, Pt,Ru, Ir, Ti, or a conductive metal oxide is coated on the memory resistor303 to form the intermediate electrode 304. A switching material layer(e.g., the switch structure 305) is formed on the intermediate electrode304, and then the hole h is filled with a top electrode material 306 a.When an oxide diode is used as the switch structure 305, the switchstructure 305 may be formed with an n-type oxide semiconductor layer anda p-type semiconductor layer. In this case, the order of stacking then-type oxide semiconductor layer and the p-type oxide semiconductorlayer may be reversed. Zn oxide or InZn oxide may be used to form then-type oxide semiconductor layer, and Cu oxide may be used to form thep-type oxide semiconductor layer.

Referring to FIG. 5E, after depositing the memory resistor 303, theintermediate electrode 304, the switch structure 305, and the topelectrode material 306 a that fills the hole h, a planarization processis performed to remove an upper portion of the material layers of thememory resistor 303, the intermediate electrode 304, the switchstructure 305, and the top electrode material 306 a, which are formed inareas other than the holes h.

Referring to FIG. 5F, an electrode material is coated on the area inwhich the hole h is formed. The electrode material is patterned to formthe top electrodes 306, thereby forming a cross point memory array.

FIGS. 6A through 6G illustrate a method of manufacturing a cross pointmemory array such as the cross point memory array shown in FIG. 1according to another example embodiment.

Referring to FIG. 6A, an electrode material is coated on the substrate300 and patterned to form the bottom electrode 301. A metal orconductive metal oxide may be used as the electrode material.

Referring to FIGS. 6B and 6C, an insulating material is coated on thebottom electrode 301. The insulating material may be coated using amethod of forming a thin film, such as spin coating, dispensing, spraycoating, etc. A nano-imprint process is performed using a stamp S inwhich a solid shape such as a circular cylinder shape, a cone shape, ora pyramidal shape is formed, thereby forming patterns having a shapeinverse to the shape of the stamp S at positions on the bottom electrode301. After performing the nano-imprint process, additional processes,such as an ashing or similar process, may be performed to expose thebottom electrode 301. When the nano-imprint process is performed, theinsulating layer 302 has a structure in which the patterns having ashape inverse to the shape of the stamp S and defining holes h areformed.

Referring to FIG. 6D, a variable resistance material is coated in theholes h to form the memory resistor 303. The memory resistor 303 may beformed of a unipolar material in which the storage and erasure ofinformation is performed by applying pulse voltages in one direction(e.g., pulse voltages having the same polarity). The unipolar materialmay be a transition metal oxide material. After the memory resistor 303is formed, a metal or conductive metal oxide is coated on the memoryresistor 303 to form the intermediate electrode 304. A switchingmaterial layer is deposited on the intermediate electrode 304 andpatterned to form the switch structure 305 on the intermediate electrode304. When an oxide diode is used as the switch structure 305, the switchstructure 305 may be formed with an n-type oxide semiconductor layer anda p-type semiconductor layer. In this example, the order of stacking then-type oxide semiconductor layer and the p-type oxide semiconductorlayer may be reversed.

Referring to FIG. 6E, portions of material layers of the memory resistor303, the intermediate electrode 304, and the switch structure 305, whichare formed between the holes h (e.g., between unit cells) are etched byperforming an etching process such as dry etching. Thus, portions of theinsulating layer 302 may be exposed. According to at least the exampleembodiment shown in FIG. 6E, the material layers between the unit cellsare removed by performing a planarization process; however the materiallayers between the unit cells may also be removed by performing anetching process.

Referring to FIGS. 6F and 6G, an insulating material, such as Si oxideor Si nitride, is coated on the exposed areas between the holes h (e.g.,on the exposed insulating layer 302) to form a passivation layer 307.

Referring to FIG. 6G, an electrode material is coated on the switchstructure 305 and is patterned to form the top electrodes 306.

As described above, when the hole h is formed using a nano-imprintprocess, the memory resistor 303, the intermediate electrode 304, andthe switch structure 305 are formed in the hole h. As a result, thenumber of etching processes may be reduced, and damage to the crosspoint memory array due to etching may also be reduced. In addition, theefficiency of a method of manufacturing cross point memory arrays may beimproved.

Hereinafter, a master for an imprint process, which may be used tomanufacture the stamp S shown in FIG. 5B or 6B, and a method ofmanufacturing the master will be described in more detail.

FIG. 7 illustrates a master for an imprint process according to anexample embodiment.

Referring to FIG. 7, a master 10 according to at least this exampleembodiment includes a 3D pattern having first type patterns h1 andsecond type patterns h2. In FIG. 7, an inclination pattern is used as afirst type pattern h1, and a vertical pattern is used as a second typepattern h2; however each of the first type patterns h1 and the secondtype patterns h2 may be an inclination pattern, a vertical pattern, arounded pattern, etc. As shown in FIG. 7, the widths of the first typepattern h1 and the second type pattern h2 are different. For example,the master 10 may have various shapes such as a shape including therounded pattern and the inclination pattern, a shape including therounded pattern and the vertical pattern, and a shape including therounded pattern, the inclination pattern, and the vertical pattern.Alternatively, the master 10 may also have a circular cylindrical shape,a cone shape, and a pyramidal shape.

The master 10 according to at least the example embodiment shown in FIG.7 is a multi-layered substrate formed of a plurality of materials. Eachof the plurality of layers may have different patterns. For example, thesubstrate may include a first layer, a second layer, and a third layer,where the second layer and the third layer are sequentially formed onthe first layer of the substrate. The first type pattern is formed inthe third layer, and the second type pattern is formed in the secondlayer. In this case, the first type pattern and the second type patternmay be an inclination pattern, a vertical pattern, a rounded pattern,etc. In addition, different patterns may be formed in a layer to formthe master 10.

Hereinafter, methods of manufacturing a master for an imprint processaccording to an example embodiment will be described in more detail withreference to FIGS. 8A through 8E, FIGS. 9A through 9E, and FIGS. 10Athrough 10E.

According to at least some example embodiments, in a method ofmanufacturing a master for the imprint process, a substrate is preparedand a mask layer exposing a portion of a surface of the substrate isformed. A first type pattern is formed by performing a first etchingprocess on the exposed surface of the substrate. A second type patternis formed in the substrate by performing a second etching process.

FIGS. 8A through 8E illustrate a method of manufacturing the master 10shown in FIG. 7 according to an example embodiment.

Referring to FIG. 8A, a multi-layer substrate 21 is prepared. Thesubstrate 21 includes a first layer 21 a, a second layer 21 b, and athird layer 21 c. The first layer 21 a may be formed of silicon, glass,or other semiconductor materials. The second layer 21 b may be formed ofsilicon oxide or nitride. The third layer 21 c may be formed of silicon.

Referring to FIG. 8B, a mask layer 22 is formed on the third layer 21 c.According to at least this example embodiment, the mask layer 22 isformed of silicon nitride or silicon oxide on the third layer 21 c. Themask layer 22 is then patterned to expose portions of the third layer 21c.

Referring to FIG. 8C, an etching process is performed on the exposedthird layer 21 c. In this example embodiment, various etching methodsmay be used. In one more specific example, an anisotropic wet etchingprocess may be performed to form inclination patterns h11. The etchingprocess is performed on the third layer 21 c until the second layer 21b, which functions as an etching stop layer, is exposed.

When the third layer 21 c is formed of Si (100), a potassium hydroxide(KOH) or tetramethylammonium hydroxide (TMAH) solution may be used toperform inclination etching, which will be described in more detailbelow.

Initially, in one example embodiment, a natural oxide layer is removedfrom the Si (100) using a solution in which a hydrofluoric (HF) solutionis diluted with deionized (DI) water at about 1:6 to about 1:10 vol %,inclusive. Anisotropic etching of Si (100) is then selectively performedusing the KOH or TMAH solution. The TMAH solution may be diluted withthe DI water at about 20 wt %, and an etching process is performed in abath of about 70° C. The etching speed in this case is about 400 nm/min.Thus, the inclination etching of Si (100) may be performed at aninclination of about 54.7°. When the third layer 21 c is formed of othermaterial than Si (100), an etching material and an etching method may beselected according to substrate materials.

Referring to FIG. 8D, an etching process such as dry etching or wetetching is performed on the exposed second layer 21 b until portions ofthe first layer 21 a are exposed to form vertical patterns h12. Forexample, when the second layer 21 b is formed of silicon oxide orsilicon nitride, the following etching method may be performed.

When the second layer 21 b is formed of silicon oxide, dry etching maybe performed as a reaction ion etching (RIE) process using a C—F-basedgas such as CF₄, C₂F₅, or C₃F₈. On the other hand, when the second layer21 b is formed of silicon nitride, a dry etching process using CF₄/CHF₃may be performed.

Referring to FIG. 8E, when the mask layer 22 is removed from thesubstrate 21, the manufacture of the master 10 for an imprint process,including the inclination patterns h11 and the vertical patterns h12formed in the substrate 21, is complete.

FIGS. 9A through 9E illustrate a method of manufacturing a master for animprint process according to another example embodiment.

Referring to FIG. 9A, initially, a multi-layer substrate 31 is prepared.According to at least this example embodiment, the multi-layer substrate31 includes a first layer 31 a, a second layer 31 b, and a third layer31 c. The first layer 31 a may be formed of silicon, glass, or othersemiconductor materials. The second layer 31 b may be formed of siliconoxide or nitride. The third layer 31 c may be formed of silicon.

Referring to FIG. 9B, a mask layer 32 is formed on the third layer 31 c.In this example, the mask layer 32 is formed of silicon nitride orsilicon oxide on the third layer 31 c and is then patterned to exposeportions of the third layer 31 c.

Referring to FIG. 9C, an etching process is performed on the exposedthird layer 31 c. In this example, vertical patterns h21 may be formedby a dry etching process. The etching process may be performed on thethird layer 31 c before the second layer 31 b is exposed.

When the third layer 31 c is formed of Si (100) and a dry etchingprocess is performed using Cl₂, CF₄, or CF₄/O₂, the vertical patternsh21 are formed in the Si (100).

Referring to FIG. 9D, drying etching of a portion of the third layer 31c is performed in a vertical direction, and then wet etching thereof isperformed to form inclination patterns h22. When the third layer 31 c isformed of Si (100), in order to perform inclination etching, a wetetching process may be performed by using a KOH or TMAH solution. Theinclination etching process may be performed until the second layer 31 bis exposed.

Referring to FIG. 9E, an etching process such as a dry etching processor a wet etching process is performed on the exposed second layer 31 bto form vertical patterns h23. For example, when the second layer 31 bis formed of silicon oxide, a C—F-based gas such as CF₄, C₂F₅, or C₃F₈may be used. When the second layer 31 b is formed of silicon nitride, adry etching process using CF₄/CHF₃ may be used when the mask layer 32 isremoved from the substrate 31. Accordingly, the manufacture of themaster for an imprint process, including 3D patterns in which thevertical patterns h21, the inclination patterns h22 and the verticalpatterns h23 are combined in the substrate 31, is complete.

FIGS. 10A through 10E illustrate a method of manufacturing a master foran imprint process according to yet another example embodiment.

Referring to FIG. 10A, initially, a multi-layer substrate 41 isprepared. According to at least this example embodiment, the multi-layersubstrate 41 includes a first layer 41 a, a second layer 41 b, and athird layer 41 c. The first layer 41 a may be formed of silicon, glass,or other semiconductor materials. The second layer 41 b may be formed ofsilicon oxide or nitride, and the third layer 41 c may be formed ofsilicon.

Referring to FIG. 10B, a mask layer 42 is formed on the third layer 41c. The mask layer 42 may be formed of silicon nitride or silicon oxideon the third layer 21 c. The mask layer 42 is then patterned to exposeportions of the third layer 41 c.

Referring to FIG. 10C, an etching process is performed on the exposedthird layer 41 c. As shown, FIG. 10C illustrates rounded patterns h31.When the third layer 41 c is formed of silicon, a wet etching processusing HF/HNO₃/H₂O or HF/HNO₃/CH₃COOH may be used to form the roundedpatterns h31. In this case, an etching process is performed on the thirdlayer 41 c until the second layer 41 b, which functions as an etchingstop layer, is exposed.

Referring to FIG. 10D, an etching process such as dry etching or wetetching is performed on the exposed second layer 41 b to form verticalpatterns h32. For example, when the second layer 41 b is formed ofsilicon oxide, a C—F-based gas such as CF₄, C₂F₅, or C₃F₈ may be used inthe etching process. When the second layer 41 b is formed of siliconnitride, a dry etching process using CF₄/CHF₃ may be performed.

Referring to FIG. 10E, when the mask layer 42 is removed from thesubstrate 41, the manufacture of the master for an imprint process,including all of the rounded patterns h31 and the vertical patterns h32formed in the substrate 41, is complete.

FIG. 11 illustrates an example embodiment of a stamp S formed using themaster 10 shown in FIG. 7.

Referring to FIG. 11, the stamp S has an inverse shape to that of themaster 10 for an imprint process. The stamp S may include inclinationpatterns S1 and protruded vertical patterns S2, which correspond tofirst and second type patterns h1 and h2 of the master 10. The stamp Sused in the nano-imprint process may be manufactured by copying patternsusing the master 10, and may also be manufactured by copying patterns bycoating a mold resin or polymer on the master 10, or by copying patternsin the form of metal by plating, or by performing a process such as anetching process after the patterns are transferred onto a quartz, glass,or Si wafer by using the master and polymer. For example, the mold resinmay be coated on the master 10, and ultra violet (UV) rays may beirradiated on the mold resin. Then, the mold resin may be cured andseparated from the master 10 to form the stamp S. In this exampleembodiment, the mold resin may include a photo initiator so as to havean UV reaction with a functionalized prepolymer including an AcrylateGroup. The mold resin may also include a releasing agent so as to beseparated from the master 10 more easily.

A master for an imprint process, according to one or more of theabove-described example embodiments, may be used to manufacture variousdevices. A stamp that is manufactured by using the master for theimprint process according to the one or more example embodiments may beused to manufacture a cross point memory array.

As described above, holes are formed in an insulating layer byperforming a nano-imprint process using a stamp formed as a masterhaving various patterns. A memory resistor, an intermediate electrode,and a switch structure that constitute a semiconductor device are formedin each of the holes. As a result, the number of etching processes maybe reduced, and damage to the cross point memory array due to etchingmay be reduced. In addition, the efficiency of the method ofmanufacturing the cross point memory array may be improved.

It should be understood that example embodiments described thereinshould be considered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each exampleembodiment should typically be considered as available for other similarfeatures or aspects in other example embodiments.

1. A method of manufacturing a cross point memory array, the methodcomprising: forming a plurality of bottom electrodes on a substrate tobe parallel with one another; forming an insulating layer on the bottomelectrodes; forming a plurality of holes through the insulating layer,each of the plurality of holes being formed at a position correspondingto a bottom electrode by performing a nano-imprint process; forming astorage node on a bottom and a sidewall of each of the holes; andforming a plurality of top electrodes to be in parallel with one anotherat positions corresponding to the holes.
 2. The method of claim 1,further comprising: removing an insulating material from the bottoms ofthe holes to expose portions of the bottom electrodes.
 3. The method ofclaim 1, wherein the forming of the storage node comprises: forming amemory resistor layer, an intermediate electrode material layer, and aswitching material layer sequentially on the bottom and the sidewall ofeach of the holes.
 4. The method of claim 3, wherein the forming of thetop electrodes comprises: depositing a top electrode material to filleach of the holes after forming the memory resistor layer, theintermediate electrode material layer, and the switching material layer;and performing a planarization process to remove portions of the memoryresistor layer, the intermediate electrode material layer, the switchingmaterial layer, and the top electrode material, which are formed inareas other than the holes.
 5. The method of claim 3, wherein the memoryresistor layer is composed of a transition metal oxide material.
 6. Themethod of claim 5, wherein the transition metal oxide material includesNi oxide, Ti oxide, Hf oxide, Zr oxide, Zn oxide, W oxide, Co oxide, Cuoxide, Nb oxide, or a material including at least one selected from thegroup including Ni oxide, Ti oxide, Hf oxide, Zr oxide, Zn oxide, Woxide, Co oxide, Cu oxide, and Nb oxide).
 7. The method of claim 3,wherein the forming of the switching material layer comprises: formingan n-type oxide semiconductor layer and a p-type oxide semiconductorlayer.
 8. The method of claim 3, wherein the forming of the topelectrodes comprises: etching portions of the memory resistor layer, theintermediate electrode material layer, and the switching material layer,formed between the holes, to expose a portion of the insulating layerafter forming the memory resistor layer, the intermediate electrodematerial layer, and the switching material layer; forming a passivationlayer by coating an insulating material on the exposed insulating layer;and forming top electrodes on the switching material layer.